The Dependence of RPM to the size of Spinning Ball Bearings
Cam, Ben
Introduction
This Experiment applied many laws of physics in order to work, among them are friction, centrifugal force and the way sound can determine speed.
Friction is the force that holds back the movement of a sliding or moving object that has come in contact with another object. Friction itself works against, or in the opposite direction to the movement of the object in motion. Friction can be measured with a unit called the coefficient of friction, or the friction coefficient. This unit helps resemble how easily one object moves in relationship to another.¹
For example, the Teflon on pans is used to create a low friction environment for cooking. This helps prevent food sticking to the bottom of the pan when it is being cooked. An example of a high friction environment could be a car tire on the road. This friction is intended to give the car traction and move it forward. It is also known that there is less friction in joints than in Teflon. This is just an example of the complexity and advanced structure of the human body. Friction itself is proportional to the load or weight that presses the to objects together. So for example, the friction of two ducks on top of each other is twice as much as just one duck.² Not much is known about frictional forces, but it is known that on a microscopic level, the reason two highly polished and smooth surfaces such as the ball bearings and the mirror that seem to not be porous are actually quite rough. You may have to zoom in a good bit, but the reason for friction is the small structures that protrude further than others make contact and create something called a “cold weld”, which is the strong attraction of intermolecular forces. This causes the spinning balls to slow down and eventually stop.
Friction plays a large role in our experiment because it is the lack therein that enables the ball to spin at such a high speed. The low friction environment of the two very smooth surfaces, the ball bearings and the concave cosmetic mirror, help reduce the friction and in turn help the balls spin faster for a longer period of time.
In reality, centrifugal force is not actually real. It can feel very real for an object in motion though. The object believes it is not moving or accelerating forward, when in fact it is. For example, the balls in our hurricane must be glued together in order to keep them from flying apart, and that epoxy must create a strong bond to absorb the force of being pushed outward. It is known that an object moving in a circular pattern, and is always accelerating, which means that it is never in an inertial frame of reference, or a coordinate plane that validates Newton’s first law. Newton’s first law states that an object in motion will stay in motion unless an external force is applied to it.
Sound- When an object vibrates; it causes the air around it to vibrate it as well. The vibrating air causes the human eardrum to vibrate and thus sound is received. When we measure the height of the sound waves, we’ll be able to get an exact measurement of the level of noise and pitch of the vibration caused by the balls moving along the mirror. Sound creates waves, and when we measure the height of these waves, we can get some idea of the speed of the spinning balls.
The purpose of this experiment is to determine the speed and rotation of two ball bearings on a smooth surface, and decide whether or not the size of the ball bearing affects the speed of the rotation. Before we started our experiment, we generated a hypothesis that the small balls would rotate faster than the large balls. The larger balls weighed more, so the friction between the balls and the mirror is increased. Because each ball weighed more, it required more force to complete its rotation. This need for force would coincidentally decrease our RPM.
Procedure
We used the metal ramp and the magnets to create a rig used to glue the two ball bearings together. It enabled the two ball bearings to be glued with minimum movement once the epoxy was applied. We set the metal ramp in an isolated area, and made sure it was level. We attached the magnets to one of the ball bearings, and had the other one ready. We applied a very small dot of two step epoxy to the center of the ball bearing with the magnets attached, and rolled the other ball bearing onto the first, and they magnetized together. We set the ball bearings aside overnight, so they could completely dry. The next day, we set up our magnifying cosmetic mirror so it was flat with the ground, and started off the ball bearing rig with a spin. We needed to be in a quiet area in order for this to work best, so we went to the computer lab. We did this because we measured the sound of the waves emitted by the bearings to determine the speed. We started with a test of three times for each rig using a regular straw. We then used the can of compressed air to help speed up the ball bearings even faster. We started by blowing for five seconds then left it for thirty seconds afterward. We repeated this three times for each rig, using Amadeus Pro to record the sound. After we collected the data, we went back to the sound recordings, and zoomed in until we found the second of spinning with the optimal speed. We then measured how often the sound fluctuated, because the balls emitted a very rapid th-thumping sound. Within that one-second, we counted the fluctuations and used those to determine the Hertz, the SI unit for frequency.
Each visible wave is counted as one Hertz.
Results
Test 1
Test 2
Test 3
Little Ball Spray
28hz
20hz
15hz
Big Ball Spray
14hz
15hz
16hz
Little Ball Straw
14hz
17hz
19hz
Big Ball Straw
10hz
15hz
14hz
Our results were as hypothesized, showing that the little ball with the compressed air had an higher frequency hertz, the fastest test being 28 hertz, therefore a faster spin. the second fastest was the big ball spray, and the third and fourth dropped according to our hypothesis. We took some pictures of the balls spinning
P-value between little ball spray and big ball spray=.252
P-value between little ball straw and big ball straw=.157
Conclusions
Our results showed that indeed, the small balls with the compressed air had the fastest hertz, with a frequency of 28 hertz. We believe the reason for the small balls being the fastest was the smaller surface area for a "cold weld" to form, and the centrifugal force created by the small balls was less powerful, enabling them to spin with less resistance outward. Although our T-tests showed that there was not a statistically significant difference in the hertz, we believe it was a matter of insufficient data, and if we were to collect more tests, we would get a more significant difference. The test worked better than we had hoped, although the epoxy was disappointingly weak. If we dropped the balls on the ground the epoxy shattered, and If we were to do this experiment again we should find a way to better to seal the two ball bearings together, such as a soldering tool or stronger epoxy. We would also find a way to better control the amount of air sprayed on the balls when they were being spun, mostly because there was an inconsistency of how and when and where we sprayed the balls or blew on them with the straw. We had an inconsistency as well with the amount of epoxy on the balls, and the distance of the laptop from the balls. Even though small, this would alter the sound being emitted from the rig. The last inconsistency we had was the small imperfections formed on the mirror from the spinning action of the balls. This caused a louder noise that affected our sound waves. Although there were many inconsistencies, the experiment was what we were hoping for in terms of success.
4. "Overview of Sound Waves by Ron Kurtus - Succeed in Understanding Physics: School for Champions." School for Champions by Ron Kurtus - Online Lessons for Those Seeking Success. Web. 19 Jan. 2012. <http://www.school-for-champions.com/science/sound.htm>.
Table of Contents
The Dependence of RPM to the size of Spinning Ball Bearings
Cam, BenIntroduction
This Experiment applied many laws of physics in order to work, among them are friction, centrifugal force and the way sound can determine speed.
Friction is the force that holds back the movement of a sliding or moving object that has come in contact with another object. Friction itself works against, or in the opposite direction to the movement of the object in motion. Friction can be measured with a unit called the coefficient of friction, or the friction coefficient. This unit helps resemble how easily one object moves in relationship to another.¹
For example, the Teflon on pans is used to create a low friction environment for cooking. This helps prevent food sticking to the bottom of the pan when it is being cooked. An example of a high friction environment could be a car tire on the road. This friction is intended to give the car traction and move it forward. It is also known that there is less friction in joints than in Teflon. This is just an example of the complexity and advanced structure of the human body. Friction itself is proportional to the load or weight that presses the to objects together. So for example, the friction of two ducks on top of each other is twice as much as just one duck.² Not much is known about frictional forces, but it is known that on a microscopic level, the reason two highly polished and smooth surfaces such as the ball bearings and the mirror that seem to not be porous are actually quite rough. You may have to zoom in a good bit, but the reason for friction is the small structures that protrude further than others make contact and create something called a “cold weld”, which is the strong attraction of intermolecular forces. This causes the spinning balls to slow down and eventually stop.
Friction plays a large role in our experiment because it is the lack therein that enables the ball to spin at such a high speed. The low friction environment of the two very smooth surfaces, the ball bearings and the concave cosmetic mirror, help reduce the friction and in turn help the balls spin faster for a longer period of time.
In reality, centrifugal force is not actually real. It can feel very real for an object in motion though. The object believes it is not moving or accelerating forward, when in fact it is. For example, the balls in our hurricane must be glued together in order to keep them from flying apart, and that epoxy must create a strong bond to absorb the force of being pushed outward. It is known that an object moving in a circular pattern, and is always accelerating, which means that it is never in an inertial frame of reference, or a coordinate plane that validates Newton’s first law. Newton’s first law states that an object in motion will stay in motion unless an external force is applied to it.
Sound- When an object vibrates; it causes the air around it to vibrate it as well. The vibrating air causes the human eardrum to vibrate and thus sound is received. When we measure the height of the sound waves, we’ll be able to get an exact measurement of the level of noise and pitch of the vibration caused by the balls moving along the mirror. Sound creates waves, and when we measure the height of these waves, we can get some idea of the speed of the spinning balls.
The purpose of this experiment is to determine the speed and rotation of two ball bearings on a smooth surface, and decide whether or not the size of the ball bearing affects the speed of the rotation. Before we started our experiment, we generated a hypothesis that the small balls would rotate faster than the large balls. The larger balls weighed more, so the friction between the balls and the mirror is increased. Because each ball weighed more, it required more force to complete its rotation. This need for force would coincidentally decrease our RPM.
Procedure
We used the metal ramp and the magnets to create a rig used to glue the two ball bearings together. It enabled the two ball bearings to be glued with minimum movement once the epoxy was applied. We set the metal ramp in an isolated area, and made sure it was level. We attached the magnets to one of the ball bearings, and had the other one ready. We applied a very small dot of two step epoxy to the center of the ball bearing with the magnets attached, and rolled the other ball bearing onto the first, and they magnetized together. We set the ball bearings aside overnight, so they could completely dry. The next day, we set up our magnifying cosmetic mirror so it was flat with the ground, and started off the ball bearing rig with a spin. We needed to be in a quiet area in order for this to work best, so we went to the computer lab. We did this because we measured the sound of the waves emitted by the bearings to determine the speed. We started with a test of three times for each rig using a regular straw. We then used the can of compressed air to help speed up the ball bearings even faster. We started by blowing for five seconds then left it for thirty seconds afterward. We repeated this three times for each rig, using Amadeus Pro to record the sound. After we collected the data, we went back to the sound recordings, and zoomed in until we found the second of spinning with the optimal speed. We then measured how often the sound fluctuated, because the balls emitted a very rapid th-thumping sound. Within that one-second, we counted the fluctuations and used those to determine the Hertz, the SI unit for frequency.
Each visible wave is counted as one Hertz.
Results
P-value between little ball spray and big ball spray=.252
P-value between little ball straw and big ball straw=.157
Conclusions
Our results showed that indeed, the small balls with the compressed air had the fastest hertz, with a frequency of 28 hertz. We believe the reason for the small balls being the fastest was the smaller surface area for a "cold weld" to form, and the centrifugal force created by the small balls was less powerful, enabling them to spin with less resistance outward. Although our T-tests showed that there was not a statistically significant difference in the hertz, we believe it was a matter of insufficient data, and if we were to collect more tests, we would get a more significant difference. The test worked better than we had hoped, although the epoxy was disappointingly weak. If we dropped the balls on the ground the epoxy shattered, and If we were to do this experiment again we should find a way to better to seal the two ball bearings together, such as a soldering tool or stronger epoxy. We would also find a way to better control the amount of air sprayed on the balls when they were being spun, mostly because there was an inconsistency of how and when and where we sprayed the balls or blew on them with the straw. We had an inconsistency as well with the amount of epoxy on the balls, and the distance of the laptop from the balls. Even though small, this would alter the sound being emitted from the rig. The last inconsistency we had was the small imperfections formed on the mirror from the spinning action of the balls. This caused a louder noise that affected our sound waves. Although there were many inconsistencies, the experiment was what we were hoping for in terms of success.
References
Works Cited
1. "Friction (physics) -- Britannica Online Encyclopedia." Encyclopedia - Britannica Online Encyclopedia. Web. 18 Jan. 2012. <http://www.britannica.com/EBchecked/topic/220047/friction>.
2."Physics4Kids.com: Motion: Friction." Rader's PHYSICS 4 KIDS.COM. Andrew Rader Studios. Web. 18 Jan. 2012. <http://www.physics4kids.com/files/motion_friction.htmll>.
3."Phun Physics - Topics." Phun Physics - Home. Web. 19 Jan. 2012. <http://phun.physics.virginia.edu/topics/centrifugal.html>.
4. "Overview of Sound Waves by Ron Kurtus - Succeed in Understanding Physics: School for Champions." School for Champions by Ron Kurtus - Online Lessons for Those Seeking Success. Web. 19 Jan. 2012. <http://www.school-for-champions.com/science/sound.htm>.
5. "Sound Waves." Media College - Video, Audio and Multimedia Resources. Web. 19 Jan. 2012. <http://www.mediacollege.com/audio/01/sound-waves.html>.